max@eros.UUCP (09/27/87)
In article <4124@pyr.gatech.EDU> kludge@pyr.UUCP (Scott Dorsey) writes: > > ... You hit something. It's trivial to design good sounding audio > equipment with tubes. It's damn near impossible to design good > transistor gear ... Arghh! This is exactly the argument I heard from my friend John, 18 years ago when we were in high school and building lots of amplifiers, he usually with tubes and I usually with transistors. His argument was, essentially, "when I just throw something together using tubes, it more-or-less-works; but if I do the same with transistors, it doesn't." (Here I am speaking of basic amplifiers like preamps and transformer-coupled power amps). Not even that statement is true, however, given -- and do NOT overlook this qualification if you respond to me -- equal background in the two technologies. John, in fact, had been introduced to electronics through vacuum tubes and had developed a solid inventory of prejudices and rules-of-thumb that didn't apply to transistors. He therefore concluded that transistors were more difficult to use. But if you understand the different devices in their own right, then it is actually much EASIER to get bipolar transistors, in particular, to bias up and exhibit predictable gain, because their critical parameters (transconductance and DC voltage bias) are largely device-independent, unlike tubes, whose circuits must sacrifice performance in order to tolerate the "personality" of each part number and each device within that part number. But a much stronger statement in favor of transistors is possible. If you actually tighten up the definition of "design" to mean not "produce something that more or less works" but rather "understand precisely what is going on," then there is no comparison between transistors and tubes as basic amplifier elements, at least among design engineers. Now I realize that these comments may largely be wasted, or misinterpreted, in rec.audio, but nevertheless let me try to state carefully the reason. Bipolar transistors in particular exhibit nonlinear large-signal terminal characteristics (Ic vs. Vbe) that are probably the most predictable and consistent nonlinearity known to electronics (as Gibbons and Horn first pointed out eloquently in 1963). Every competent designer is aware that, as a result, a bipolar stage with 1 mA collector current at 27 degrees C will have a gm of 38.5 mmho and a base-emitter (DC input) voltage of very nearly 0.6 or 0.7 volt. Vacuum tubes also exhibit a large-signal nonlinearity of the same critical kind, but its very *shape*, let alone numbers, depends on device construction, unit-unit variation, and age. It is not even possible to predict stage gain and DC bias in the same way as with bipolar devices, and therefore, unless you lard the circuit through with trimmers and align it periodically, you actually are *stuck* at the level of "producing something that more or less works" -- brute force, not true design. This is why, if you move beyond the level of circuits-that-more-or-less-work, there is much less argument in favor of tubes, even in simple amplifiers. There are also, of course, whole genres of audio circuits that can be constructed with bipolars that have no antecedent in tubes, owing to the precise predictable I-V characteristic of the transistors. I am speaking of things like "translinear" circuits (which can give a fundamentally linear -- not just approximately, or corrected-with-feedback) large-signal input-output relationship; or the precise variable-gain amplifiers (a subject dear to my heart) on which depend such products as Dave Blackmer's (the db in dbx) companding and noise-reduction systems. I'm responsible for a few other such circuits myself. The converse is not true, since most anything you can accomplish with triodes or pentodes can also be done with JFETs or MOSFETs. These devices share some of the gain and DC-bias predictability problems of tubes, but much less so, because the I-V characteristics are mathematically simpler, can be better controlled, and do not change with age. True, it is harder to get output swings above about 50 volts p-p, with common small-signal transistors than with tubes, but then you rarely need to. Since you can get transistors with audio-band voltage noises less than 100 nV RMS (which is to say, 140 dB down from a one-volt line level), you can still achieve a lot of dynamic range with a "mere" 50-volt output capability. Kludge continues: > ... With modern tubes and design methods microphonics and > self-oscillation aren't anywhere near the problems that > they used to be. I question this: the 12AX7's, 12AU7's, 12AT7's, 6L6's etc. that are so dear to tubophiles now are not only the same devices used in the 1950s and 60s, but in many cases actually were themselves built in the 1950s and 60s. Microphonics in particular are a function of the tube design. Perhaps Kludge designs his own tubes; if so, he's the first such designer I've met (on the other hand, I design my own transistors: it's cheap and pretty easy). I would not for a moment question someone's preference for the sound of a tube preamp or power amp (even if it is more expensive, less reliable, and has an uncertain future as existing VT stocks get burnt out, or used by enthusiastic suburban kids as BB-gun targets). Also, I am not talking about the relative ease of designing good transformer-coupled tube amps and direct-coupled solid-state amps (except to note that direct-coupled TUBE amps are also tricky). However, the broad statement that "transistor amplifiers are harder to design than tube amplifiers," unless qualified in the sense of "harder *for me*," is naive and not supported by hard facts. Incidentally, my friend John, who argued that tube circuits were "easier to design" 18 years ago, recanted that position after broader experience (he now designs analog ICs for a living). Max Hauser / max@eros.berkeley.edu / ...{!decvax}!ucbvax!eros!max
kludge@pyr.gatech.EDU (Scott Dorsey) (09/27/87)
In article <1895@ucbcad.berkeley.edu> max@eros.UUCP (Max Hauser) writes: >I question this: the 12AX7's, 12AU7's, 12AT7's, 6L6's etc. that >are so dear to tubophiles now are not only the same devices used >in the 1950s and 60s, but in many cases actually were themselves >built in the 1950s and 60s. Microphonics in particular are a function >of the tube design. Perhaps Kludge designs his own tubes; >if so, he's the first such designer I've met (on the other hand, >I design my own transistors: it's cheap and pretty easy). A 12AX7 that is twenty years old is apt to have a very different internal structure than one constructed today. In general, most of the important parameters are the same, but some things have changed, things like support members to prevent microphonics, things like filament- cathode coupling, etc. It's true that microphonics are a function of the tube design, but the fact that two tubes have the same designation number does not mean that the design is identical, unfortunately. >I would not for a moment question someone's preference for the sound >of a tube preamp or power amp (even if it is more expensive, less >reliable, and has an uncertain future as existing VT stocks get burnt >out, or used by enthusiastic suburban kids as BB-gun targets). >Also, I am not talking about the relative ease of designing good >transformer-coupled tube amps and direct-coupled solid-state amps >(except to note that direct-coupled TUBE amps are also tricky). What do you need in a stereo? You need a good power amp. A rather simple thing to design using the 'brute force' approach; use big output tubes running down near the linear end of their curve, use big output transformers (and put them in the feedback loop, please), and some form of relatively quiet driver (BY7 video pentode, AX7, etc.). That's about it. But to design a transistor amp, you need a lot of rather sneaky tricks to keep waveform symmetry, try and soup up the slew rate, and a lot of time is going to have to be spent to make it sound really good. You also need a preamp. Okay, I admit it, I use Analog Devices chips for the high-gain input stuff. They're pretty low noise, easy to work with, and cheap. And they are certainly easier to deal with for a high gain application than tubes are. But the equalization stuff and the tone control stuff is all tube, for the same reasons described under the power amp section. You also probably need a signal source. I've got a tube tape deck, because I couldn't afford a newer one. It's pretty clean, and the amount of amplifier noise is independant of the signal level (which is not true with transistors, frustratingly). But there's an integrated dbx box attached, and an all-IC CD player next to it. It's not hard to build a spectacular direct-coupled, resistively- coupled, capacitively-coupled, etc. tube amp. Look in the RCA Receiving tube Handbook. It requires a lot less tinkering than even the RCA people claim. The only transformers in my stereo are in the output of the power amp and in the power supplies. >However, the broad statement that "transistor amplifiers are harder >to design than tube amplifiers," unless qualified in the sense of >"harder *for me*," is naive and not supported by hard facts. If this is true, why are there so few good transistor power amps out there? Why are there so few good transistor preamps out there? Why isn't there any good tuner of any sort out there? -- Scott Dorsey Kaptain_Kludge SnailMail: ICS Programming Lab, Georgia Tech, Box 36681, Atlanta, Georgia 30332 Internet: kludge@pyr.gatech.edu uucp: ...!{decvax,hplabs,ihnp4,linus,rutgers,seismo}!gatech!gitpyr!kludge
jtn@potomac.UUCP (John T. Nelson) (09/28/87)
So can't amplifiers be constructed so that they use the best
attributes of both tubes and transistors? Are the two technologies so
mutually exclusive that an amp must be either one or the other?
--
John T. Nelson UUCP: rutgers!mimsy!rlgvax!sundc!potomac!jtn
Advanced Decision Systems Internet: jtn@ads.arpa
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Ubks@unisoft.UUCP (Brian K. Shiratsuki) (09/28/87)
In article <1996@potomac.UUCP> jtn@potomac.UUCP (John T. Nelson) writes: >So can't amplifiers be constructed so that they use the best >attributes of both tubes and transistors? Are the two technologies so >mutually exclusive that an amp must be either one or the other? the NYAL moscode amplifiers are just such a hybrid, using vacuum tubes up to the output stage, where there are mosfets (``moscode'' <- mosfet + cascode). i believe the power supply is also solid state. couldn't find an NYAL dealer around here to listen to one, anyone know of an NYAL dealer in the bay area? -- brian
georgep@vice.UUCP (10/02/87)
In article <1996@potomac.UUCP>, jtn@potomac.UUCP (John T. Nelson) writes: > So can't amplifiers be constructed so that they use the best > attributes of both tubes and transistors? Are the two technologies so > mutually exclusive that an amp must be either one or the other? > (I can't resist) How about a nice FET in a glass envelope!!!! geo
kludge@pyr.gatech.EDU (Scott Dorsey) (10/03/87)
In article <1941@vice.TEK.COM> georgep@vice.TEK.COM (George Pell) writes: >In article <1996@potomac.UUCP>, jtn@potomac.UUCP (John T. Nelson) writes: >> So can't amplifiers be constructed so that they use the best >> attributes of both tubes and transistors? Are the two technologies so >> mutually exclusive that an amp must be either one or the other? >How about a nice FET in a glass envelope!!!! Hm.. It's almost like a nuvistor in reverse. We could call them 'Oldvistors.' Sell a lot to high-end audio people. Make a lot of money, then retire to the Bahamas and buy a Kenwood. Yeah... -- Scott Dorsey Kaptain_Kludge SnailMail: ICS Programming Lab, Georgia Tech, Box 36681, Atlanta, Georgia 30332 Internet: kludge@pyr.gatech.edu uucp: ...!{decvax,hplabs,ihnp4,linus,rutgers,seismo}!gatech!gitpyr!kludge
georgep@vice.TEK.COM (George Pell) (10/05/87)
In article <4155@pyr.gatech.EDU>, kludge@pyr.gatech.EDU (Scott Dorsey) writes: > In article <1941@vice.TEK.COM> georgep@vice.TEK.COM (George Pell) writes: > >How about a nice FET in a glass envelope!!!! > Hm.. It's almost like a nuvistor in reverse. We could call them > 'Oldvistors.' Sell a lot to high-end audio people. Make a lot of > money, then retire to the Bahamas and buy a Kenwood. Yeah... All right! You contact the glass blowers, I'll get a hold of Motorola. Anybody know where we can get some octal sockets? The price on these things have got to be right, say $250.00 each, or no one will buy them. geo
kludge@pyr.gatech.EDU (Scott Dorsey) (10/07/87)
In article <1949@vice.TEK.COM> georgep@vice.TEK.COM (George Pell) writes: >All right! You contact the glass blowers, I'll get a hold of Motorola. >Anybody know where we can get some octal sockets? The price on these >things have got to be right, say $250.00 each, or no one will buy them. Make sure you get gold-plated octal sockets. They either sound so much better or cost so much more that people aren't willing to admit that they really don't sound better. And check the FETs out to assure people that they are getting a matched pair. -- Scott Dorsey Kaptain_Kludge SnailMail: ICS Programming Lab, Georgia Tech, Box 36681, Atlanta, Georgia 30332 Internet: kludge@pyr.gatech.edu uucp: ...!{decvax,hplabs,ihnp4,linus,rutgers,seismo}!gatech!gitpyr!kludge
franka@mntgfx.MENTOR.COM (Frank A. Adrian) (10/07/87)
In article <1941@vice.TEK.COM> georgep@vice.TEK.COM (George Pell) writes: |In article <1996@potomac.UUCP>, jtn@potomac.UUCP (John T. Nelson) writes: |> the best attributes of both tubes and transistors? |How about a nice FET in a glass envelope!!!! Don't forget the little LED for that friendly little glow!!!!!!!! Frank "I want a few pF's too" Adrian Mentor Graphics, Inc.
jaym@nuchat.UUCP (Jay Maynard) (10/08/87)
In article <4155@pyr.gatech.EDU>, kludge@pyr.gatech.EDU (Scott Dorsey) writes: > In article <1941@vice.TEK.COM> georgep@vice.TEK.COM (George Pell) writes: > >In article <1996@potomac.UUCP>, jtn@potomac.UUCP (John T. Nelson) writes: > >> [tubes vs. transistors in the same amp] > >How about a nice FET in a glass envelope!!!! I thought that's what tubes were...GlassFETs. > Hm.. It's almost like a nuvistor in reverse. We could call them > 'Oldvistors.' Sell a lot to high-end audio people. Make a lot of > money, then retire to the Bahamas and buy a Kenwood. Yeah... There might even be enough to afford that nice new TS-940S you're looking at. No tubes, either. (oops...this isn't rec.ham-radio...sorry about that :-) -- Jay Maynard, K5ZC (@WB5BBW)...>splut!< | temporarily at uunet!nuchat!jaym Never ascribe to malice that which can | while splut is down (@#*(&$% ST4051!!) adequately be explained by stupidity. | GEnie: JAYMAYNARD CI$: 71036,1603 The opinions herein are shared by neither of my cats, much less anyone else.
mat@mtx5a.ATT.COM (m.terribile) (10/12/87)
> In article <1941@vice.TEK.COM> georgep@vice.TEK.COM (George Pell) writes: > |In article <1996@potomac.UUCP>, jtn@potomac.UUCP (John T. Nelson) writes: > |> the best attributes of both tubes and transistors? > |How about a nice FET in a glass envelope!!!! > Don't forget the little LED for that friendly little glow!!!!!!!! If you want to sell on the audiophile market, you really should get a blue glow in there; everybody will assume it's a new variation on the Beam Power Tube. Convince them that it's a new Ballistic Transport (Beam Power?) FET. If you have to use a LED, then use green, but be sure to use one that has a clear plastic lens so that people can't identify it for what it is. (That green illumenator LED used behind the power indicator on the Olivet######AT&T PCs should do the job.) -- from Mole End Mark Terribile (scrape .. dig ) mtx5b!mat (Please mail to mtx5b!mat, NOT mtx5a! mat, or to mtx5a!mtx5b!mat) (mtx5b!mole-end!mat will also reach me) ,.. .,, ,,, ..,***_*.
cgs@umd5.umd.edu (Chris Sylvain) (10/20/87)
In article <2017@mtx5a.ATT.COM< mat@mtx5a.ATT.COM (m.terribile) writes: << In article <1941@vice.TEK.COM< georgep@vice.TEK.COM (George Pell) writes: << .. Don't forget the little LED for that friendly little glow! < < If you want to sell on the audiophile market, you really should get a blue < glow in there ... Blue glow did you say? Try a Blue LED. ... Don't laugh, it's a REAL product looking for a market. Needs about 3.5V across it. It's made from silicon nitride, and is available in small quantities. They're more a curiousity than anything else, as no one has come upon a good reason for needing a Blue LED. The company that makes them (silicon nitride is really tough stuff; hard to work with) is Japanese.. Masushita (sp?), if I'm remembering the name correctly. -- --==---==---==-- .. Beware the Jabberwock, my son! .. ARPA: cgs@umd5.UMD.EDU BITNET: cgs%umd5@umd2 UUCP: ..!uunet!umd5.umd.edu!cgs
larry@kitty.UUCP (Larry Lippman) (10/21/87)
In article <2002@umd5.umd.edu>, cgs@umd5.umd.edu (Chris Sylvain) writes: > < If you want to sell on the audiophile market, you really should get a blue > < glow in there ... > > Blue glow did you say? Try a Blue LED. ... Don't laugh, it's a REAL product > looking for a market. Needs about 3.5V across it. It's made from silicon > nitride, and is available in small quantities. They're more a curiousity > than anything else, as no one has come upon a good reason for needing a > Blue LED. The company that makes them (silicon nitride is really tough > stuff; hard to work with) is Japanese.. Masushita (sp?), if I'm remembering > the name correctly. There are off-the-shelf blue LED's available from Siemens Components, Optoelectronics Div. (who absorbed Litronix, formerly a major optoelectronics manufacturer). The Siemens P/N is LDB5410, and the illumination is blue at a wavelength of ~ 480 nm. The lamp is in a T1-3/4 package. The Vf is close to 4.0 volts. The fabrication technology is silicon carbide. We have used these LED's as an internal light source in some scientific instruments for quite some time. They look neat as panel lamps, but that's not the reason why we use them. You can buy them through Hamilton-Avnet. So, now y'all can be the first on your block with blue LED's... :-) <> Larry Lippman @ Recognition Research Corp., Clarence, New York <> UUCP: {allegra|ames|boulder|decvax|rutgers|watmath}!sunybcs!kitty!larry <> VOICE: 716/688-1231 {hplabs|ihnp4|mtune|seismo|utzoo}!/ <> FAX: 716/741-9635 {G1,G2,G3 modes} "Have you hugged your cat today?"
mikkel@cg-atla.UUCP (Carl Mikkelsen) (10/21/87)
In article <2002@umd5.umd.edu> cgs@umd5 (Chris Sylvain) writes: > >Blue glow did you say? Try a Blue LED. ... Don't laugh, it's a REAL product >looking for a market. Needs about 3.5V across it. It's made from silicon >nitride, and is available in small quantities. They're more a curiousity >than anything else, as no one has come upon a good reason for needing a >Blue LED. The company that makes them (silicon nitride is really tough >stuff; hard to work with) is Japanese.. Masushita (sp?), if I'm remembering >the name correctly. > > ARPA: cgs@umd5.UMD.EDU BITNET: cgs%umd5@umd2 > UUCP: ..!uunet!umd5.umd.edu!cgs I am looking for such a LED! Does anyone have any further leads? I've talked with HP and some other opto sources without luck. Thanks, Carl +--------------------------+--------------------------------+ | Carl Mikkelsen | ..!ism780c\ | | | ..!cbosgd!ima>!cg-atla!mikkel | | Compugraphic Corporation | ..!ulowell/ | | 200 Ballardvale St. | ..!decvax/ | | Wilmington, Ma. 01887 | (617) 658-5600 x 5220 (voice) | | | (617) 658-0200 x 5220 (TT-auto)| +--------------------------+--------------------------------+
king@dciem.UUCP (Stephen King) (10/22/87)
In article <2002@umd5.umd.edu> cgs@umd5 (Chris Sylvain) writes: >Blue LED. The company that makes them (silicon nitride is really tough >stuff; hard to work with) is Japanese.. Masushita (sp?), if I'm remembering >the name correctly. > I beg to differ. Blue LED's are made by Siemens in Europe (originally), although the Japanese may have them now also. (Matsushita) ...sjk -- * Defence & Civil Institute * ...!utzoo!dciem!king * of Environmental Medicine * Stephen J King - Simulation & Training Group - (416) 635-2149
howard@cpocd2.UUCP (Howard A. Landman) (10/22/87)
In article <2017@mtx5a.ATT.COM> mat@mtx5a.ATT.COM (m.terribile) writes: >If you want to sell on the audiophile market, you really should get a blue >glow in there; everybody will assume it's a new variation on the Beam Power >Tube. [...] If you have to use a LED, then use green, [...] Why not blue? Blue-light LEDs (made with, I believe, silicon carbide) are readily available, just a little expensive. For this application, cost is clearly not a major factor. Now if HP would just release a blue version of their 101-LED bar graph display (currently available in red and green) ... -- Howard A. Landman {oliveb,hplabs}!intelca!mipos3!cpocd2!howard <- works howard%cpocd2%sc.intel.com@RELAY.CS.NET <- recently flaky howard%cpocd2.intel.com@RELAY.CS.NET <- ??? try this
ross@raster.UUCP (Ross Werner) (10/26/87)
>In article <2017@mtx5a.ATT.COM> mat@mtx5a.ATT.COM (m.terribile) writes: >>If you want to sell on the audiophile market, you really should get a blue >>glow in there; everybody will assume it's a new variation on the Beam Power >>Tube. [...] If you have to use a LED, then use green, [...] You guys are really behind. The Bedini power amp beat you all to it. They grind off the TO-3 cans on the power transistors (by hand, of course!) and fill them with some "proprietary crytalline substance" that "improves transient speed" and lots of other such bull. AND THEY GLOW IN THE DARK! New! Improved! The speed and punch of transistors! The warm glow of tubes! The manufacturer is in southern California - maybe that explains it. Ross (I'm allowed to make jokes about southern CA, I grew up there.)
pete@tcom.stc.co.uk (Peter Kendell) (10/29/87)
in article <935@cpocd2.UUCP>, howard@cpocd2.UUCP (Howard A. Landman) says: > > Why not blue? Blue-light LEDs (made with, I believe, silicon carbide) are > readily available, just a little expensive. For this application, cost is > clearly not a major factor. > > Now if HP would just release a blue version of their 101-LED bar graph > display (currently available in red and green) ... The only application I have ever seen for blue LEDs is the full-beam indicator in the instrument cluster of a VW Polo (and presumably other models too). Red, green and blue... Why have no manufacturers that I've heard of tried to make a large-scale full-colour TV display with these beasts? -- ------------------------------------------------------------------------------ | Peter Kendell <pete@tcom.stc.co.uk> | | ...{uunet!}mcvax!ukc!stc!pete | ------------------------------------------------------------------------------